Temperature control system



A ril 18, 1939. H. R. CRAGO TEMPERATURE CONTROL SYSTEM Filed Sept. 21, 1955 Inventor". Harvg R- CroLgo,

His Attorney.

Patented Apr. 18, 1939 UNITED STATES TEMPERATURE CONTROL SYSTEM Harry R. Crago, Caldwell, N. J., assignor to General Electric Company, a corporation of New York Application September 21, 1935, Serial No. 41,577

11 Claims.

The invention relates to temperature control systems, particularly systems employed in air conditioning or other temperature regulating service in which a plurality of inter-related temperatures are selectively controlled in accordance with predetermined conditions.

One of the principal objects is to provide an improved temperature control system wherein joint or separate operation of a plurality of temperature regulating means may be obtained under the selective control of a plurality of thermostats responsive to variations in different predetermined temperature conditions.-

Although the broad principle of the invention is of general application, a special object is to provide an improved control for an air conditioning system having a room thermostat and a three position selective temperature thermostat for jointly and separately controlling the operation of an electrically controlled air circulating and conditioning apparatus and an electrically controlled automatically fired boiler furnace provided with a steam coil for heating the circulated air. In such a system the air circulating and the heated air to regulate the temperature of a room or other space to a desired value and the furnace is operated to regulate the temperature of the circulated air. To avoid discomfort due to circulation of air, it is desirable to start operation of the air circulating and conditioning apparatus only when the condition of the furnace is such as to maintain the air temperature above a comfortable minimum value. In case the condition of the furnace is not such as to maintain the air above the minimum desired temperature value, it is desirable to start operation of the furnace only upon a call for heated air from the room thermostat. Furthermore',,it is desirable to insure continued operation of the furnace when once started until it is in condition to insure a continued supply of heated air over a substantial interval of time and thus improve the efliciency of combustion by avoiding repeated starting and stopping of the automatic burner apparatus as may occur in the operation of the air circulating and conditioning apparatus. 7

The present invention provides improved means for selectively transferring control of both the starting and the stopping of operation of the air circulating and conditioning apparatus and of the furnace between the thermostat responsive to the room temperature and the three positionselective thermostat responsive to a temperature :5 condition dependent upon the furnace in accordconditioning apparatus is operated to transfer ance with predetermined relations between said temperatures so as to provide the desired sequential operation of the apparatus as outlined above.

While the principle of the present invention may be employed with advantage in other tem- 5 perature control service such as with cooling apparatus or other forms of heating systems, the single figure of the accompanying drawing diagrammatically shows the invention embodied in a room air conditioning system for purposes of 10 illustration and explanation of the principle thereof.

As shown in the drawing the air conditioning apparatus I0 is provided with a blower ll driven by the electric motor I 2 for circulating the air 15.

from the cold air return duct l5 to the hot air distributing duct IS. A finned air heating coil or radiator l1 and a humidifying device I8 both located in space B inside the air conditioner ID are provided for conditioning the circulated air. 20

The electrically controlled oil fired boiler furnace 20 supplies steam to the air heating coil I! so as to heat the air which is circulated by the blower ll through the distribution duct ii. The boiler furnace 20 is provided with suitable electric motor driven pumping apparatus 2| for supplying oil together with high pressure atomizing air and low pressure combustion air to the burner head 22 and low pressure combustion air to the lower air box 23. Suitable means including the 30 spark electrodes 24 are provided for igniting the atomized oil to start combustion in the furnace. Operation of the air conditioning apparatus In and the automatic oil fired boiler furnace 20 is selectively controlled by the two thermostats Ti 35 and T2. The thermostat T1 is located in a space or room A to which heated air is supplied through duct I6 from the air distribution conduit It as indicated by the dotted lines in the drawing to regulate the temperature of said space. 0

The room thermostat T1 is shown provided with a suitable bimetallic thermostatic element 21 which operates between two limiting positions It and S in response to variation in the temperature of the space A from a predetermined-value. For 5 heating service the position R is the cold position and the'position S is the hot position, the mid position in which the element 21 is shown being that corresponding to the desired temperature in the space A which the thermostat T1 is adjusted to maintain. I The thermostat T: which may be designated as the heat exchange or three position selective thermostat is shown as of the type having the expansible operating bellows 30 connected to the conditioner ingcoil [1 so as to be responsive to the variations in the temperature thereof. The bellows 30 operates against the bias of spring 32 to move the contact 33 between three positions indicated as C, I, H which correspond respectively to the cold, the intermediate and the hot temperatures of the heating coil [1.

The improved selective control provided by the present invention enables the thermostats T1 and T2 to effect selective starting and stopping of operation of the air conditioner l and the furnace 20 under the following combinations or relations of temperature conditions.

1. With the heat exchange thermostat T2 in either position I or H. indicating that the coil I1 is in condition for effectively heating the circa-- lated air, operation of thermostat T1 to position R.

\lv'ill szeparately start the motor driven blower 2. With thermostat T2 remaining in either position I or H, subsequent operation of thermostat T1 to position S will separately stop the operation of the motor driven blower ll--|2.

3. With thermostat T2 in position C indicating lack of, sufficient heat in the coil I! to effectively heat the circulated air, operation of the room thermostat T1 to position R will effect the separate starting of the furnace 20 to supply the required heat to the coil ll.

4. With operation of the furnace 20 once started in accordance with condition 3, as soon as the temperature of the coil I1 is raised to the value to effect operation of the thermostat Tz'to position I, the operation of the motor blower H-| 2 of the air conditioner I0 is then started. Under this condition the operation of furnace 20 -is continued jointly with operation of the airconditioner l0. p

5. Under the joint operating condition 4, when the operation of the furnace 20 has supplied suflicient heat to the coil IT to effect operation of thermostat T2 into position H, the operation of the furnace 20 is separately stopped while the operation. of the motor blower ll-l2 is con-' tinued.

6. If during joint operation of the air conditioner and the furnace under condition 4, the supply of heated air to space A becomes sufiicient to cause operation of thermostat T1 from position R into position S, the operation ofv the motor driven blower |ll2 of the air conditioner I0 is separately stopped while the operation of the furnace 20 is continued.

"I. In case during joint operation of the air III and the furnace 20 under condition 4, the temperature of the heating -coil I! should decrease so as to cause operation of thermostat T: from position I to position C, the operation of the air conditioner I0 is separately stopped while the operation of the furnace 20 is continued.

8. Under condition I, in case the separate operation of the air conditioner l0 should reduce the temperature of the air heating coil I1 sufliciently to effect operation of thermostat T2 into position C, then further operation of the motor driven blower H-|2 of the air conditioner I0 is separately stopped and operation of the furnace 20 is separately started.

As will be pointed out more specifically hereinafter the air humidifying apparatus I8 is arranged to be operated under the control of a device Ho which is responsive to the humidity of the air in the space A only when the motor driven follows.

the boiler furnace switches 40 and 45 to start and tube 3| which is located in contact with the heatfan ll, I2 of the air conditioner Ill is'in operation.

The preferred form of selective control apparatus illustrated in the drawing which is operated by the two thermostats T1, T11 under the different combinations of temperature conditions outlined above is constructed and. arranged as An electromagnetic switch 40 is pro.- vided with a contact 4| for closing and opening a circuit for energizing the motor l2 of the air conditioner from the electric power supply line L1, L2. provided with the movable contact 46 for closing a circuit to energize the electrical operating mechanism 2| of the furnace 20 from the supply lines L L2. A third thermostat T3 has the expansible bellows 48 arranged to operate the movable contact 45 of electromagnetic switch 45 independently of the energization of electromagnetic switch 45. The bulb 49 of the thermostat T3 is responsive to the temperature of the water in theboiler furnace 20. 'The thermostat T3 serves to operate the contact to automatically start and stop operation nism 2| so as always to maintain the water in 20 above a predetermined Another electromagnetic switch 45 is of the burner mecha minimum value. This value is only slightly belowthe steaming temperature so that the water temperature may be quickly raised to supply steam to the air heating coil l'I whenever the electromagnetic switch 45 is energized. A transfer relay 50 is provided for cooperating with the thermostat T1 and T1 in the selective control of the energization of the electromagnetic stop operation of the air conditioner I0 and the furnace '20.

A transformer 60 serves to provide a low voltage source of energizing currentffor the electromagnetic switch 40 and the relay 50. A separate transformer 62 serves to provide a low voltage source of current for energizing the electromagnetic switch 45. An electric motor driven clock mechanism C is continuously energized from terminals Y and R, of transformer 52 and is arranged to shift thecalibration setting of thermostat T1 between the day and the night range in any well known manner.

The detailed operation of the apparatus under the several conditions previously outlined is as follows. Under condition I, as long as the temperature of the air heating coil I1 is sufficiently high so that the contact 33 of selective thermostat T2 is in either position I or H, movement of contact 21 of room thermostat T1 into position R starts separate operation of the air conditio ing apparatus l0 in the following manner. A circuit is establishedfrom the terminal R of the low voltage secondary winding of the transformer 60 through conductors 10, ll contacts R and 21 of thermostat T1 conductor 12, contact 5| of the transfer relay 5!! in its lower position, conductor 13, the operating winding of relay 40 and thence through conductor 14 to terminal B of transformer 60. The energization of the operating winding of switch 40 serves to operate contact 4| from the open position to which it is biased as shown to close the energizing circuit for the motor l2. This starts operation of the air circulating blower ll. At the same time the auxiliary contact 43 closes to establish a holding circuit for maintaining the operating winding of switch 40 energized from the terminals B and R. of transformer 60' which is independent of the original energizing circuit through the thermostat T1 but extends through contact 5| of trans-t fer relay 5!).

. The operation the blower I [by th motor I! serves to draw/airthroughthe"return duct l5 which may -bejjconnected with the spacejfa and circulates the air over the finned'air heat. ing coil I! and through the distributing duct l6 and the duct 16' indicated'by the dotted lines connected to space A. This serves to transfer heat from" the space B toth'e space A to regulate the temperature of the space A.

At any time during operation of the motor driven blower ll l2 of theair conditioner ID, in case the humidity of the air in the space 'A is such that the contacts of the humidity responsive device He are closed, thereupon an energizing circuit for the electromagnetic water supply valve V is completed in order to supply water to the humidifying device l8. This imparts humidity to the air, in space B. The valve energizing circuit extends'from the. terminal h of transformer 60 through the contacts of the humidity responsive device Hc, conductor 80, and thence through valve V to conductor I3 which is always connected during operation of the fan to the terminal R of transformer 60.. The winding RL of the transformer provides a higher voltage suitshort circuit extends from conductor (4 through the upper contact 52 of the relay 50', conductor 8!, contact 21 of thermostat T1 in position S and thence through conductor 12, contact 5|, and conductor 13 to the other side of the operating winding of switch 40. This results in deenergiz ing the switch so as to return contacts 4| and 43 to theirrespective open positions in which they are shown. The opening of contact 4| stops operation of motor I! and the opening of contacts 43 opens the energizing circuit of valve V to stop the supply of water to the humidifying device l8.

Operation under condition 3 occurs when the temperature of the air heating coil I1 is reduced to the value whichcauses operation of contact 33 of the selective thermostat T2 into positionC. With contact 33 in position C, an energizing circuitfor the transfer relay 50 is established, this circuit extending from the transformer terminal B through conductor 14, the operating winding of the transfer relay 5!], contact 33 in position C and conductors 83 and I0 to transformer terminal R. Relay 50 operates to move'its contact 5| from the lower position to its upper position and at the same time open the contact 52. The movement of contact 5! to its upper position results in transferring the control of thermostat T1 from the starting switch 40 of the air conditioning apparatus to the starting switch 45 of the furnace 20. -Thus with thermostat T1 in position R and contact 5| of transfer relay 50 in its upper position, an energizing circuit for the operating winding of starting switch '45 is com-- pleted from the terminal R1 of transformer 52 through conductors Ill and H, contact 2 in position R, conductor 12;"c'ontact 5| iii-its upper poto supply properly conditionedair in the sp'ac 'stoppeclv by operation of contact '33 of thermostat sition, conductors and 86, the operating wind-g1: ing of switch'45 and conductor 81 to terminal B2 of transformer 62; Whenthu's energizedthe switch 45 operatesthe contact 48' to 'energize the" oil"burnermechanism'2l-of the boilerfurnace l 20 from the supply lines L1,-Lz throughconductors 83 and .This starts operation of the 'oil burner mechanism to establish combustion in the furnace soas use raise .the temperatureofthe water in the boiler'to the steaming point and thereby supplysteam to raise the temperature of the air heating coil l1. Upon closure of switch 45; the auxiliary contact 41 thereof establishes a holding circuit directly from the transformer terminal R1 through conductor 90. This insures that-the burner mechanism 2| when once started into operation continues to supply heat to the coil 1! until the temperature thereof is sufiicient to operate contact 33 of thermostat T2 into position In position H, the operating winding of switch 45 is short circuited by the contact 33 thereby stopping operation of the burner mechanism as will be outlined under condition 5. Operation under condition 4 ordinarily will follow operation undercondition 3 as justIdescribed. As soon as the operation of the burner mechanism 2| under condition 3 has served-to, raise the temperature of the air heating coil l1 sufficiently to cause operation of contact '33 of thermostat T2 fromposition C into position I, then the operating winding of transfer relay 50 will be deenergized. This results in the return of contact 5| to its lower position in accordance withits bias and also the closure of contact52'. Upon the returnof contactjl to its lower posi tion, the energizing circuit for switch, 40 which was described under condition 1 is again com-. o pleted.- Thereupon switch operates 'to ener-, gize the motor I2 for driving the air circulating blower II and also to start a supply of J water'to 4 the humidifying apparatus 18 in case the humidi stat He indicates adeficiency of humidity inthe" space A; Thus under conditions! both ;th" ejfurnace and the air conditionerare in operatic f' Operation under condition occurs whenever during joint operation of furnace 201a'nd air ditioner ID, as in condition}, the temperature of ,v the air heating coil l 1 is; increased sufficiently to cause operation of contact 33 of thermostat T2 into position H in which the operating ing of switch 45 is short circuited through c n'- ductors as and s1. Thisdeenergizes the s t 45 and contact 46. is opened to deener'giz burner mechanism .Z- l.'. At lthe same 'time'a xi iary contact 41 opens theholding circuit. Operation under "condition 6,will occu during joint operation of the ,air congitio l and the furnace 20 under condition 4,'thesupply of heated air to space A becomes suflicient to; cause operation of [thermostat T1 from position'j R into position S. With contact 21 of thermostat 4 T1 in position S, ashort circuit for the operating winding of switch 40 is established, this'cirv cuit extending from ,oneterminal of the operating winding through conductor l3,switch;5l its lower position, conductor 12', contact 2] in'position S, conductor 8| and switch 52, to the other terminal of the operating winding; w ergizes the switch 40 and contactl opens to'dj 1 energize motor l2, However, it will be under; stood, that the burner mechanism 2| of fur nace ;2li will always continue in operationlunti T2 in position H as described under condition 5 85 eration of the motor blower H,

, 50 so as to operate contact 5| to, stop operation of the air conditioner and start operation of the 10 furnace. Under these conditions the movement of contact 5| from its lower. position serves to interrupt the holding circuit for the operating windingcf switch 40' extending through auxiliary contact 43 and conductors I5 and 16, there- 15 by deenergizing' the switch to open contact 4| and deenergize motor It. The movement of contact 5| into its upper position serves to energize switch 45' and thereby start operation of the burner mechanism 2| in the manner described 2 0 under condition 3. I

Operation under condition 8 occurs in case during operation under condition 1, the separate operation of the motor blower H, I! of the air conditioner Ill should-reduce the temperature 25 of the air heating coil l'l sufliciently to effect operation of contact 33 of thermostat T2 into position C. This serves to energize the transfer relay 50 so as to stop operation of the air conditioner and start operation of the furnace in the man-.

80 ner described under condition 7. It will be understood, however, that due to the heat storage capacity of the water in boiler furnace 20, the air heating coil ll will be'maintained heated for an, appreciable interval of time during separate op- H of the air conditioner. Thus in mild weather the air conditioner may be'operated repeatedly under the control of the room thermostat T1 without causing thetemperature of the air heating coil I! to decrease belowthevalue at which the selective thermostat T operates to start operation of the furnace; The selective control provided by the present inventi'oninsures that the burner mechanism 2| of furnace 20 is operated when once started over a considerable period so as to store an appreciable amount of heat in the boiler water. This heat then maybe-distributed in small increments by repeated operation of the motor blower ll, 12- of thank conditioner In to the room without requiring further operation of the automatic furnace. At the same time the selective control of the present invention effectively prevents the circulation of cold air by'the operation of the 55 air conditioner at any time.

of the invention is particularly advantageous in air conditioning systems of the character, described above, it will be apparent to those; skilled in the art that it may be applied with-equal ad- 60 vantage in other temperature regulatingiservice.

What -I claim as new and desire to, secure by Letters Patent of the States, is; 1. In a temperaturecontrol systemythe com bination of apparatus operablefor circulating a I! of the air conditioner l0 "While the principle to the temperature of said medium for controlling operation of said transfer device and having a separate stop control connection with said temperature varying apparatus independent of said transfer device.

2. In a temperature control system, the combination of means operable for transferring heat between two spaces to regulate the temperature of one of said spaces, separate means operable for regulating the temperature of the other space, a thermostatic device responsive to the temperature of said one space and having a start connection provided with a selective device for selectively and separately starting operation of each of said means at a predetermined temperature in said one space and having a separate stop connection for said heat transfer means controlled by said transfer device, and a second thermostatic device responsive to the temperature of said other space for controlling the operation of said selective device and having a separate stop connection for said separate means independent of said transfer device.

3. In a temperature control system, the combination of means operable for transferring heat between two spaces to regulate the temperature of one of said spaces, separately operable means for regulating the temperature of the other space,

a-thermostatic device responsive to the temperature of said one space and having separate start and stop connections for controlling the operation of said heat transfer means, a second thermostatic deviceresponsiveto the temperature of said other space and having a stop connection for controlling the stopping of operation of said second means, and control transfer means operable under the control of said second device for ling the starting of operation of a selected one 0 of said means when the temperature of said space is at one of said limiting values and the stopping of operation of said first means when the temperature of said space is at said other limiting value, and a second thermostatic device responsive to the temperature of said other space connected to stop operation of said separately operable means when the temperature of said other space reaches the upper limiting value and having a selective two-position relay con-- trolled thereby and interconnected with said first thermostatic device for selectively controlling the starting and stoppin of operation of said first transferring the start connection of said firstv heat transfer medium to regulate-a temperature I temperature or. a-thermostatic con-i, attan-and having control transfer device foperable-Lto v -'con'trol elementfrom said-.circulating-apparat means and-the starting of operation of said sepcondition, apparatus ".ODGIQbIQ to regu'late the "limiting value. 1

7o connections 1min ram .ren 1 control connection of said thermostatic bination of electrically controlled means operable to said temperature varying apparatusga 75 second thermostatic control elementresponsive ond'space-to regulate "the temperature of said arately operable means'in' accordance with vari- Li ations in the temperature ofsaid. other space j "between'said intermediate value and the lower.

-5. In a temperature control system,.the-

or' varying thet'emperature of a space, separate lectrically controlled means operable for transih'eat betw'eensaid first space and a. sec-.

second space, a first thermostatic control device operable between two circuit closing positions upon opposite variations in the temperature of said first space, a second thermostatic control device operable between two circuit closing positions upon opposite variations in the temperature of said second space, a circuit selective relay operated from one position to another position upon operation of said first thermostatic control device to a predetermined one of its positions, circuit connections established in said one position of said relay whereby said second control device in one position thereof controls the starting of operation of said second means and in the other position thereof controls the stopping of operation of said second means, circuit connections established in the other position of said relay whereby said second control device controls in said one position thereof the starting of operation of said first means, and circuit connections whereby operation of said first control device to its other position effects stopping of operation of said first means. 6. In a temperature control system, the combination of means for transferring heat betweenone space and another space, means operable for varying the temperature of said one space, a first thermostat responsive to the temperature of said one space, a second thermostat responsive to the temperature of said other space, means including a-selective device operable under the control of said first thermostat upon variations in the temperature of said one space for selectively rendering said second thermostat effective to control the starting of operation of each of said means when the temperature of said other space is at a predetermined value and the stopping of operation of said first means when the temperature of said other space is at a higher value, said device being operable under the control of said first thermostat for stopping operation of said one means independently of said second thermostat, and separate means under the exclusive control of said first thermostat for stopping operation of said other means.

7. In a temperature control system, the combination of means operable for transferring heat between one space and another space, means oper'able for varying the temperature of said one space, a thermostat responsive to the temperature of said one space, a thermostat responsive to the temperature of said other space, a selective device operable between two positions under the control of said first'thermostat and interconnected with said second thermostat for jointly therewith starting separate operation of a corresponding one of said means in each position of said device and stopping operation of only one of said means upon operation of said device from the corresponding position to the other position thereof and thereby insure starting joint operation of said means in a predetermined sequence, and separate means under the exclusive control of said first thermostat for stopping operation of the other means. 7

8. In a temperature control system, the combination of means operable for transferring heat between one space and another space, means operable for varying the temperature of said one space, a thermostatic control elementoperable between three control positions in response to variations of the temperature of said one space, a second thermostatic control element operable between two control positions in response to variations of the tanperature of said other space. a

selective control device operable under the control of said first thermostatic device and interconnected with said second control element for starting separate operation of said first means when said first and second control elements are inpredetermined positions, and for starting operation of the other of said means when said second control element is in said predetermined position and said first control element is in a difierent position and for stopping operation of said one means and starting operation of said other means upon operation of said first control element from said difierent position to said predetermined position.

9. In a temperature control system, the combination of an automatically controlled device for varying a predetermined temperature condition, said device having energizing means and separate .deenergizing means, a second automatically controlled device for varying a second temperature condition in heat transfer relation with said predetermined temperature condition, said second device having energizing means and separate deenergizing means, and control means'including a first thermostatic element operable responsively to variations in said predetermined temperature condition between two positions for controlling the energizing means of either one of said automatically controlled devices in one position thereof and the separate deenergizing means of said first electrically controlled device in the other position thereof, and a second thermostatic element operable responsively to .variations in said second temperature conditions between two positions and having a selective device controlled thereby for selectively rendering said first element effective for controlling either the energizing and 'deenergizing means of said first'device or the energizing means of said second device and to a third position for controlling the separate deenergizing means of said second device.

10. In a room air conditioning system, the combination of a thermostat responsive to the temperature of a room and movable between a hot and a cold position, an air conditioner having an air heating coil and an electric motor driven. blower for circulating air to said room, an automatically fired boiler furnace for supplying heat to said air heating coil, a second thermostat responsive to the temperature of said air heating coil and movable between a hot, an intermediate and a cold position, a two-position circuit selecl tive relay connected to be operated upon operation of said second thermostat between said intermediate and said cold positions and a plurality of separately operable control relays connected with said selective relay and said thermostats and operable selectively to start operation of said furnace with both of said thermostats in their cold position and continue operation of the furnace independently of movement of the room thermostat to its hot position until said second thermostat moves into its hot position, to start operation of said blower with the first thermostat in the cold position and the second thermostat in either the intermediate or hot position, and to stop operation of the blower whenever the first thermostat moves into its hot position or the second thermostat moves into its cold position. a r

- 11. In a room air conditioning system, the combination of means'operable to circulate the air, means for heating the circulated air including an automatic burner mechanism, and means for selectively controlling the starting of sepa- I tions,

rate operation of the air circulating means and 7/ the burner and the starting of joint operation thereof in a predetermined sequence including a room thermostat having only two control posia selective thermostat operable between three control'positions in accordance with variations in the temperature of the air heating means, a two-position transfer relay controlled by operation of said selective thermostat between two of said control positions and having connections for connecting the room thermostat in one posi- HARRY R. CRAGO. 

